The processing of data regarding the three-dimensional shape of a dental replacement may be done by means of a CAD (computer-aided design) system, which may be part of a CIM (computer-integrated manufacturing) system. Such systems are made available, for example, by 3M ESPE AG (Seefeld, Germany) under the name LAVA™, for the production of ceramic bridge copings. With this known LAVA™ system, the CAD system is connected to an optical scanner and to an NC-milling machine. The scanner captures the three-dimensional surface of a dentition impression and passes on the captured data to the CAD system. Using the CAD system, the operator can modify these surface data as desired, so as to draw up the three-dimensional shape of the bridge coping, calculate CNC data from the shape data using CAM software, and then send the corresponding CNC data to the NC-milling machine. The NC-milling machine then processes, for example, a zirconium oxide or zirconia ceramic blank as precisely as possible in agreement with the shape data.
At a dentist, an impression is produced from the situation in the mouth of the patient. This impression is used by a dental technician to prepare a positive saw cut model of the situation in the patient's mouth. The positive model is typically made from gypsum or light plaster. This positive model thus corresponds to the teeth in the patient's mouth. Conventionally, the positive model is then sent to a milling center where it is scanned and milled, as described above.
In some situations, e.g., with a 4-unit bridge, it is often difficult for the technician in the milling center to determine the exact and optimal position and dimension of the bridge units as well as the necessary reinforcement or the correct arrangement of the copings. This is, however, an important factor for an optimal facing with veneer porcelain in terms of stability, function, and aesthetics. If the positioning of the bridge units is not correct, the design of the dental replacement may need to be reworked, e.g. virtually modified in the milling center, and a new replacement milled, which can add considerably to the cost of producing the replacement.